Journal of Economic Entomology (2020) 113, 612-621

Venkatesan G. Sengoda, Xiangyang Shi, Rodrigo Krugner, Elaine A. Backus and Hong Lin (2020)
Targeted mutations in Xylella fastidiosa affect acquisition and retention by the glassy-winged sharpshooter, Homalodisca vitripennis (Hemiptera: Cicadellidae)
Journal of Economic Entomology 113 (2), 612-621
Abstract: Xylella fastidiosa (Wells) is a xylem-limited bacterium that causes Pierce's disease of grapevines. The bacterium is transmitted by insect vectors such as the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar). Experiments were conducted to compare the role of selected X. fastidiosa genes on 1) bacterial acquisition and retention in GWSS foreguts, and 2) transmission to grapevines by GWSS. Bacterial genotypes used were: mutants Xf-ΔpilG, Xf-ΔpilH, Xf-ΔgacA, and Xf-ΔpopP; plus wild type (WT) as control. Results showed that Xf-ΔpilG had enhanced colonization rate and larger numbers in GWSS compared with WT. Yet, Xf-ΔpilG exhibited the same transmission efficiency as WT. The Xf-ΔpilH exhibited poor acquisition and retention. Although initial adhesion, multiplication, and retention of Xf-ΔpilH in GWSS were almost eliminated compared with WT, the mutation did not reduce transmission success in grapevines. Overall, Xf-ΔgacA showed colonization rates and numbers in foreguts similar to WT. The Xf-ΔgacA mutation did not affect initial adhesion, multiplication, and long-term retention compared with WT, and was not significantly diminished in transmission efficiency. In contrast, numbers of Xf-ΔpopP were variable over time, displaying greatest fluctuation from highest to lowest levels. Thus, Xf-ΔpopP had a strong, negative effect on initial adhesion, but adhered and slowly multiplied in the foregut. Again, transmission was not diminished compared to WT. Despite reductions in acquisition and retention by GWSS, transmission efficiency of genotypes to grapevines was not affected. Therefore, in order to stop the spread of X. fastidiosa by GWSS using gene-level targets, complete disruption of bacterial colonization mechanisms is required.
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Database assignments for author(s): Xiangyang Shi, Rodrigo Krugner, Elaine A. Backus, Hong Lin

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Xylella fastidiosa	Grapevine (Vitis)	U.S.A. (SW)
	Homalodisca vitripennis	Grapevine (Vitis)	U.S.A. (SW)